Synthetic monocrystalline rutile



United States Patent Cfifice 2,693,421 Patented Nov. 2, 1954 SYNTHETIC MONOCRYSTALLINE RUTILE William G. Eversole and Wilfred Drost, Kenmore, N. Y., assignors, by mesne assignments, to Union Carbide and Carbon Corporation, a corporation of New York No Drawing. Application March 22, 1949, Serial No. 82,928

14 Claims. (Cl. 106-42) This invention relates to red single crystals of synthetic rutile, and to a method for making such crystals.

Single crystals of rutile have only recently been produced synthetically by periodically passing small amounts of titania powder axially down through an oxy-hydrogen flame onto a support which is aligned axially with such flame, and causing the material melted in the flame to crystallize progressively by gradually moving the flame and support apart axially of the flame. The general procedure is similar to the process for making synthetic sapphire disclosed by Verneuil in U. S. Patent 988,230, and similar apparatus is used. When pjure titania powder is used, the crystal is black, opaque, and unsuitable for use as a gemstone.

The object of the present invention is toproduce a red single crystal of synthetic rutile which is suitable to be cut and used as a gemstone.

In accordance with the present invention, a black single crystal of synthetic rutile is grown from a powder mixture consisting of titania (TiOz) and a minor amount of at least one substance selected from the group consisting of vanadium oxide (V205) and chromium oxide (C1203) by fusing the powder in an oxy-hydrogen flame and allowing the fused material to crystallize progressively, in accordance with Verneuils teachings with reference to sapphire. Preferably the chromium oxide and/or vanadium oxide should be present in an effective amount up to about 1% of the mixture by weight.

The black rutile crystal is then heated in an atmosphere of oxidizing gas such as oxygen, whereupon it is converted to a red crystal which is suitable for cutting into a gemstone. The temperature during this step desirably is maintained above 300 C. but below the melting point of rutile. The preferred temperature range is from 600 C. to 1300" C.

In an example of the invention, a short thick black rutile boule weighing about 80 carats was grown successfully from a powder mixture consisting of TiOz and about 0.1% of CrzOs. This boule was then oxidized by heating it in a furnace for ten hours at 1150" C. in an atmosphere of oxygen, whereupon the color was converted to red.

In a second example a black rutile boule was grown successfully from a powder mixture consisting of TiOz and about 0.01% V205. This boule was then oxidized for ten hours at 1150 C. in an atmosphere of oxygen, whereupon the color was converted to red.

What is claimed is:

1. A single crystal of synthetic rutile consisting of titania and an effective amount up to about 1% of at least one substance selected from the group consisting of vanadium oxide and chromium oxide.

2. A red single crystal of synthetic rutile consisting of titania and an effective amount upto 1% of chromium oxide.

3. A red single crystal of synthetic rutile consisting of titania and about 0.1% of chromium oxide.

4. A red single crystal of synthetic rutile consisting of ttania and an effective amount up to 1% of vanadium 0x1 e.

5. A red single crystal of synthetic rutile consisting of titania and about 0.01% of vanadium oxide.

6. A method for synthesizing a single crystal of rutile which can be converted to a red color by heat treatment in an oxidizing atmosphere, said method comprising fusing a powder consisting of titania and an effective amount up to 1% of at least one substance selected from the group consisting of vanadium oxide and chromium oxide, and crystallizing the fused material as a single crystal.

7. A method for synthesizing a red single crystal of rutile comprising fusing a powder consisting of titania and an effective amount up to 1% of at least one substance selected from the group consisting of vanadium oxide and chromium oxide, crystallizing the fused material as a single crystal, and heating the crystallized material in an atmosphere of oxidizing gas.

8. A method for synthesizing a red single crystal of rutile comprising fusing a powder consisting of titania and about 0.1% of chromium oxide, crystallizing the fused material as a single crystal, and heating the crystallized material in an atmosphere of oxidizing gas.

9. A method for synthesizing a red single crystal of rutile comprising fusing a powder consisting of titania and about 0.01% of vanadium oxide, crystallizing the fused material, and heating the crystallized material in an atmosphere of oxidizing gas.

10. A method for growing a single crystal of rutile which can be converted to a red color by heat treatment in an oxidizing atmosphere, said method comprising periodically passing axially through a flame and melting therein a powdered composition consisting of titania and an effective amount up to 1% of at least one substance selected from the group consisting of vanadium oxide and chromium oxide, accumulating and crystallizing the material so melted as a single crystal on a support aligned axially with such flame, and moving such flame and support apart axially of such flame.

11. A method for making a red single crystal of rutile comprising periodically passing axially through a flame and melting therein a powdered composition consisting of titania and an effective amount up to 1% of at least one substance selected from the group consisting of vanadium oxide and chromium oxide, accumulating and crystallizing the material so melted as a single crystal on a support aligned axially with such flame, moving such flame and support apart axially of such flame, and subsequently heating the crystallized material in an atmosphere of oxygen at a temperature between 300 C. and 1300 C.

12. A single crystal of synthetic rutile consisting of titanium dioxide and 0.1% of an oxide of vanadium.

13. A single crystal of synthetic rutile consisting of titanium dioxide and 0.1% of an oxide of chromium.

14. A composition of matter for synthesizing single crystals of rutile consisting of a fusible powdered mixture of titania and an effective amount up to about 1% of at least one substance selected from the group consisting of chromium oxide and vanadium oxide.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 988,230 Verneuil Mar. 28, 1911 2,311,917 Wainer et a1. Feb. 23, 1943 2,371,660 Wainer Mar. 20, 1945 

1. A SINGLE CRYSTAL OF SYNTHETIC RUTILE CONSISTING OF TITANIA AND AN EFFECTIVE AMOUNT TO ABOUT 1% OF AT LEAST ONE SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF VANADIUM OXIDED AND CHROMIUM OXIDE. 